1. Field of the Invention
This invention relates to a fuel feeding system connected in a closed loop circulation system to a plurality of direct fired burners in which fuel is supplied to the burners in accordance with burner capacity to consume the fuel.
2. Description of the Prior Art
It is known that finely ground coal can be utilized in burners, much as a liquid fuel, provided the coal is reduced in size so that it acts in a substantially fluid manner. Examples in the prior art include the control system for feeding fuel to furnaces where pulverizing apparatus is provided for reducing the coal so that it acts as a fluid in a carrier stream of air. The example is disclosed in Dickey U.S. Pat. No. 2,172,317 of Sept. 15, 1939 and in Dickey U.S. Pat. No. 2,439,721 of Apr. 13, 1948. Other examples of apparatus for grinding coal for direct coal fired burner systems are disclosed by Williams in U.S. Pat. No. 4,184,640 of Jan. 22, 1980, and U.S. Pat. No. 4,226,371 of Oct. 7, 1980, and in copending application of Williams, Ser. No. 530,632 filed Sept. 9, 1983.
The problem which exists in direct fired multiple coal burners is one which involves maintaining a proper coal-to-air ratio for each burner and the usual application is to supply all of the ground coal and air into a single burner. However, there is a problem with multiple burners in that it is not possible to take any of the burners out of service without causing the system to shut down. The ability to turn on or turn off various burners in a multiple burner system is desirable, especially in fluid bed combustors or power plants, but that ability has not been made available before now.